The optics and electronics industries rely upon inorganic compounds for fabrication of various components. However, these industries have frequently ignored the many benefits that may be obtained when employing organic compounds. It has been recently recognized that organic compounds with delocalized pi-electron systems may exhibit large nonlinear optical responses. In many cases, the responses are larger and more favorable than those displayed by inorganic counterparts.
Of the many potential applications of organic compounds to the industries mentioned above, many relate to the electro-optic effect as described by Kerr (1875) and Pockels (1906). Additionally, frequency doubling by second harmonic generation (SHG) is often considered. SHG may be defined as the doubling of lights fundamental frequency.
A test to study SHG has been developed (Kurtz and Perry, 1968) which analyzes, for instance, the noncentrosymmetric crystal structure of organic compounds. Organic compounds which possess a noncentrosymmetric structure exhibit optical nonlinearity and are generally said to be nonlinear.
Organic nonlinear chemical compounds displaying high SHG properties are potentially useful in applications which require high speed optical modulators. Such applications include high speed long distance data links and electric field sensors for use in electromagnetically noisy environments. In addition, such materials provide efficient wavelength shifting capability for optical and infrared remote sensing (e.g., of pollutant particulate concentration) and diode laser frequency doubling for optical data storage.
The known processes for producing nonlinear organic chemical compounds, such as stilbazolium salts, require piperidine (often in excess amounts) as a catalyst. Piperidine is the catalyst of choice because it generally produces acceptable reaction rates in alkylation reactions. Use of piperidine to produce the nonlinear organic chemical compounds described herein is a major obstacle. This is true because piperidine is a highly controlled and regulated chemical substance since it is a well known precursor for phencyclidine (PCP).
The present invention, therefore, is based on the discovery of a process for producing stilbazolium salts without requiring piperidine as a catalyst. An additional embodiment of the instant invention is the use of a heterocyclic amine catalyst that unexpectedly results in increased reaction rates and product yields. In the instant invention, the stilbazolium salts produced are substantially pure wherein substantially pure is defined as at least about 95% pure.